Andromeda
The relatively peaceful Commonwealth has fallen at the hands of the Nietzcheans, who see themselves as Nietzsche's ubermenschen. The only one who can save civilization, Dylan Hunt, is frozen for 300 years on the event horizon of a black hole before he finally escapes and leads a rag-tag crew. Sharp, thought-provoking writing from Deep Space Nine veteran Robert Hewitt Wolfe and others helped this show stand out, especially in its first couple of years.
Quatermass
Spiritual father to Doctor Who, Nigel Kneale's 1950s science hero was as unmistakably British as the stories he starred in, offering conversation and compassion at a time when American SF heroes would rather blow up any monsters than try to reason with them.
The 4400
4400 people kidnapped at different points in time by mysterious beings return to the present day with cool superpowers. How will they integrate themselves back into society, and who kidnapped them in the first place? This twisty, weird, awesome show featured Jeffrey Combs and Summer Glau and was like a good cross between X-Files and Heroes.
Supernatural
The Winchester Brothers aren't just sworn to hunt down the monsters that disturb the normal people — they're also doomed. Sam is cursed from birth, and Dean is trapped living in their father's image. As they wander the barren landscape of the Midwest, this often terrifying, often hilarious show never lets us hope the brothers will escape their doom — just keeps us wondering what they'll do in the face of it.
Alien Nation
Long before District 9 subjected aliens to apartheid, Alien Nation used extraterrestrial visitors to explore issues of immigration and race. The Newcomers, former alien slaves who escaped to Earth in hopes of a better life, just want to integrate with human society while holding on to their own cultures and traditions. However, as human cop Matthew Sikes and his Newcomer partner discover, many humans hate, fear, and exploit the Newcomers.
Robotech
The show that helped introduced space opera to a whole new generation (along with Starblazers), Robotech gave us humans struggling against not one, but three alien invasions, using bootstrapped alien technology. And more importantly — super robot armor.
Lexx
As if on a mission to out-camp Star Trek's original run, Lexx brandishes its technicolor sassiness with pride. Marty Simon's soundtrack for the series shines - and while you can snicker all you want at the CGI, many of the computer rendered shots are on par with those from contemporary series Babylon 5. Besides, who doesn't love a hot half-lizard rebel love slave?
The Avengers
Simultaneously stylish and silly, this British spy-fi show left its mark on the sixties and managed to keep sputtering on into the seventies, thanks to a spin-off series. The bowler-hat-wearing John Steed has a variety of sidekicks, but the catsuit-clad Emma Peel is the only one anyone remembers — for good reason. Not only was she a fashion icon, she always seemed to be in on Steed's joke.
RoswellSexy teen aliens with problems is a formula for greatness. Katherine Heigl burst out into our consciousnesses, playing an alien human hybrid stuck on Earth, along with her friends. Trapped in Roswell, NM (What are the odds) these clones of alien royalty discover they have superpowers, and a lot of teen drama ensues. A highlight of the series home town diner waitress Liz Parker played by Shiri Appleby and her alien antennae work attire. It was like Dawson's Creek, but with aliens — so yes, it worked on many levels.
Quantum Leap
Let's hear it for blue unitard time-jumping. When Sam Beckett, played by a young Scott Bakula, gets lost in time after a failed experiment, he winds up body-jumping through the ages. And each body has its own problems and issues that Sam has to help him/her through. But he's not alone — his best friend, Al the hologram, appears from time to time to smoke cigars and drop some wisdom. The best part of this series is its cliffhanger endings, which almost always end up with Sam in a dress.